MacViews: All targets compile. Fixes unit_tests and message_center_unittests

This mainly involves adjusting chrome_tests_unit.gypi to exclude
chrome's unit_tests that use views UI not enabled by default with
toolkit-views=1 on Mac.

Mostly the unit tests compile, but fail to link since their
corresponding UI parts are not in the browser.
(confirm_bubble_views_unittest.cc has a simple compile fix, but isn't
linked in yet).

An events_test_support dependency is needed in views_test_support for
ui/events/test/event_generator which some unit tests use, and otherwise
comes in through aura_test_support or views_unittests.

BUG=412234, 399191

Review URL: https://codereview.chromium.org/507373002

Cr-Commit-Position: refs/heads/master@{#294047}
diff --git a/ui/message_center/BUILD.gn b/ui/message_center/BUILD.gn
index 536bcfc0..b05d402 100644
--- a/ui/message_center/BUILD.gn
+++ b/ui/message_center/BUILD.gn
@@ -76,7 +76,9 @@
       deps += [ "//ui/aura" ]
     }
 
-    if (toolkit_views) {
+    # On Mac, toolkit-views builds still use the Cocoa UI. Keep this in sync
+    # with message_center_unittests below.
+    if (toolkit_views && !is_mac) {
       sources += [
         "views/bounded_label.cc",
         "views/bounded_label.h",
@@ -209,7 +211,7 @@
       deps += [ "//ui/gfx:test_support" ]
     }
 
-    if (toolkit_views) {
+    if (toolkit_views && !is_mac) {
       sources += [
         "views/bounded_label_unittest.cc",
         "views/message_center_view_unittest.cc",